Transmitting antenna with automatic tuning, particularly for aircraft wireless



June 14, 1949. v H. KAPPELER 2,472,904

v TRANSMITTING ANTENNA WITH AUTOMATIC TUNING,

PARTICULARLY FOR AIRCRAFT WIRELESS Filed Jan. 20, 1945 rov8ni01 2 ,J -H. apgzter patented June 14, 1949 TRANSMITTING ANTENNA WITH AUTO- MATIC TUNING, PARTICULARLY FOR AIRCRAFT WIRELESS Hans Kappeler, Soleure, Switzerland, assignor to the firm Autophon Aktiengesellschaft, Soleure, Switzerland, a joint-stock company of Switzerland Application January 20, 1945, Serial No. 573,702 In Switzerland December 24, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires December 24, 1963 3 Claims. (Cl. 250-33) This invention relates to transmitting antennae with automatic tuning, particularly for aircraft radio sets.

There exist antennae, especially for aircraft radio sets, which are tuned manually or by remote control. These tuning methods have several inconveniences. Manual tuning requires special concentration of the radio operator on the amperemeter for the antenna current during transmission. With pre-tuning, carried out when the aeroplanes are on the ground, serious detuning can occur. Moreover, these remote-controlled antenna devices, in which tuning is carried out by a variable coil for increasing the effective length of the antenna, or by a condenser for decreasing the effective length, must be put at an easily accessible place., Then the antenna is often in an unfavorable position with regard to radiation.

The invention relates to a transmitting antenna, the tuning of which to the maximum antenna current at the selected frequency is effected automatically by a motor drive controlled by the antenna current and operating to vary the length of the antenna.

The accompanying drawing illustrates diagrammatically, by way of example, one embodiment of the object of the invention.

The installation according to the invention consists essentially of three parts, viz.: the highfrequency part, the motor drive and the control device. The connections y and z are connected to the output of the transmitter, namely: y to the anode of the terminal stage and z to the core of the transmitter. In order to simplify the drawing and increase clearness, said output of the transmitter is not shown. The condensers C4 and C5 form a capacitive potential divider for the antenna coupling to the transmitter. Between the two condensers is a connection to the primary side of the current transformer STW which is also connected to the sliding contact SK, which latter performs the electric connection to the antenna A coiled around the drum T, which antenna is weighted at its free end by a weight G. The secondary winding of the current transformer STW is in the circuit of the rectifier tube V1, wherein R1 represents a working resistance and C1 a condenser. To improve the direct current, this current is led to the tube V2 over a smoothing filter which consists of the resistances R2 and B3 and the condensers C2 and C3. The

anode of the tube V2 is connected with regard to direct current, over the anode resistance R, to the positiveelement of a battery .(notshown),

whereas with regard to alternating current itis connected, in the illustrated position of the contact 82, over the condenser C to ground. In the second position of contact .92, the polarized rel'ay P is connected between the condenser C and ground, whereby the working contact 101 of said relay is arranged in the control device.

The motor drive consists mainly of the motor M which aotuates, over the coupling KP and a self-locking worm gear Sgl, the shaft W on which the drum T is arranged. Another self-lockin worm gear Sg2, arranged on the same shaft, represents the connection to the cam disc NS which forms a part of the control device andwill be mentioned again in connection therewith. The release magnet Kpm actuates, over the twoarmed lever H which is rotatably arranged atD, the coupling K10 and controls in this way the drive of shaft W. The spring F effects the return of the coupling into the released position as soon as magnet Kpm is released.

The control device consists essentially of the three relays L, K and S and the contacts l1, l2, 13; k1, its, 704; $1 and s2 appertaining respectively thereto, the relay being indicated by a capital letter and its working contacts indicated by the corresponding small letter in each instance. Contact 82 of relay S is arranged in the high-frequency part whereby a connection between the control device and the high-frequency part is provided. The push-button switch DS controls the contacts m-s, whereas the switch HS, controlling thet contacts 11-3, is connected mechanically to the non-illustrated main switch of the whole arrangement. Another connection between the high-frequency part and the control device is brought about the contact m which is a working contact operated by relay P1. The connection of one side of each of the relays S, K and L, to the negative element of a non-illustrated battery, as well as the connections. of the above mentioned working contacts appertaining thereto and of the contacts (21-3 and 11-3 is clearly shown in the drawing and their functions will be explained more in detail when explaining the working of the installation according to the invention. The control device further includes the cam disc NS belonging to the worm gear Sg2, which disc is provided with cams U and V in whose paths of rotation spring lamellae Fu and F1; protrude. These spring lamellae actuate associated contacts, namely spring lamella F1) actuates contact '01 and spring lamellav Fu actuates contacts til-3.

The manner of operation of thisinstallation,

beginning with it in rest position, is as follows: The contacts a1 3 are interconnected with the usual frequency selecting mechanism of the radio set in such manner that upon selection of a frequency by the operator the contact a1 is momentarily closed, and contacts a2 and as are momentarily opened. Relay L is thereby energized, is held by current supplied over contact Z1, and closes the contacts l2, la. The motor M and the magnet Kpm for closing the coupling KP are thereby supplied with current and the drum T and the worm gear S92 are driven by means of the worm gear Sgl in a direction for unwinding the antenna A. When the latter is entirely uncoiled, switch as is momentarily engaged by means of the cam or pin U, and the associated contacts m, as are thereby closed. Relay L is de-energized and its contacts Z1 3 are opened. Relay K is energized over the circuit comprising the positive terminal contacts m, 141;, as and negative terminal Relay S likewise receives current over the positive terminal contacts 1'2, uk, and negative terminal Relay K is held by current supplied over the positive terminal contacts a2, 111,231,161 and ne ative terminal Relay S is likewise energized and held by current supplied over the positive terminal -i-, contacts a2, '01, p1, 101, 1'3, s1, and negative terminal The polarized relay P, by the change-over of cont-act s2 of relay S, is put into circuit over the condenser C.

The energizing of relay K closes the contacts k3, hi, and thereby reverses the direct current motor M so that it rotates the drum T in the opposite direction to wind up the antenna. As the length of the antenna approaches a resonance point of the frequency selected and the negative voltage on the grid of the tube V2 increases, the condenser C is charged over the resistance R. As soon as the resonance point is exceeded by a small amount, and in consequence thereof, the negative tension on the grid of tube V2 is reduced, condenser C discharges through the tube V2 and the polarized relay P is dc-energized and opens the contact 171. Relays K and S are de-energized. Contacts R1, 765, kr are opened, the motor M stops, the coupling KP is disengaged. The length of the antenna is thereby automatically adjusted to correspond to the frequency for which the radio transmitter is set. The non-reversing worm gears So! and S92 hold the drum T against rotation and thereby prevent a detuning of the antenna by outside influences. Through the de-energizing of relay S, the contacts s1, 83 are opened and s2 changes-over in order that the condenser C can be charged. On a new change in frequency, the contacts (11 are again momentarily closed and a2, as momentarily opened. The tuning process begins anew by unwinding the antenna A as described below.

On disconnecting the radio apparatus or on letting down the landing gear, the contacts 12 and T3 are momentarily opened in a non-illustrated manner and contact r1 momentarily closed. Relay K is energized and is held by current supplied over contact In; contacts 763, k4 are closed, the motor is supplied with current, so that the antenna is Wound up until cam V opens contact in and effects the de-energizing of relay K. Opening the contacts k1, its and k4 results in a stopping and uncoupling of the motor M.

It will thus be seen that the apparatus in accordance with the invention operates to unreel the antenna when the radio set is put into operation, automatically adjust the length of the antenna to the frequency of the radio set and wind up the antenna when the radio set is turned off or the aircraft is about to land.

What I claim is:

1. In combination with an aircraft radio transmitter having frequency tuning means, a trailing antenna connected with the output of the transmitter, a reel for the antenna, a reversible motor for rotating the reel to reel the antenna in and out, switching means activated by tuning of the transmitter to supply power to said motor for reeling the antenna out, switching means activated by the reeling of the antenna out to a pre-- determined limit for reversing the direction of rotation of the motor to reel the antenna in, a current transformer having its primary winding connected in series with the transmitter output, a trip circuit connected with the secondary of said transformer and responsive to changes in the amperage of antenna current and a relay operable by said trip circuit to cut off power from said motor to stop the reel upon passage of the antenna current amperage through a maximum value.

2. In combination with an aircraft radio transmitter having frequency tuning means, a trailing antenna connected with the output of the transmitter, a reel for the antenna, means for rotating the reel in one direction to reel the antenna in and in the opposite direction to reel the antenna out, switching means controlling the rotation of said reel and activated by tuning of the transmitter to reel the antenna out, switching means activated by the reeling of the antenna out to a predetermined limit for reversing the direction of rotation of the reel to reel the antenna in, a current transformer having its primary winding connected in series with the transmitter output, a trip circuit connected with the secondary of said transformer and responsive to changes in the amperage of antenna current, a relay operable by said trip circuit to stop the reel upon passage of the antenna current amperage through a maximum value, and means for holding the reel in adjusted position to prevent detuning of the antenna by outside influences.

3. In combination with an aicraft radio antenna having frequency tuning means, a trailing antenna connected with the output of the transmitter, a reel for the antenna, means for rotating the reel in one direction to reel the antenna out to increase its'length and in the opposite direction to reel the antenna in and decrease its length, a control circuit for said reel rotating means including switching means activated by tuning of the transmitter to initiate rotation of the reel in a direction to unreel the antenna, a holding device to continue the unreeling of the antenna and switching means activated by the unreeling of the antenna to a predetermined length for reversing the direction of rotation of the reel to reel the antenna in, a current transformer having its primary connected in series with the transmitter output, a trip circuit connected with the secondary of said transformer and comprising a triode, a rectifier connected with the secondary of said transformer and with the grid of said triode to apply a negative bias to said grid proportional to the antenna current, a polarized relay nd a condenser and means for connecting the relay and condenser in series between the anode of the triode and ground during the reeling in of the antenna in such manner that upon passage of the antenna current amperage through a maximum value the negative s bias on the grid of the triode is reduced permitting the condenser to discharge through the tube and actuate said relay, and connections between said relay and the control circuit for stopping the reel upon actuation of the relay in said manner, whereby the reeling in of the antenna is automatically stopped when the antenna is of proper length.

HANS KAPPELER.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Name Date De Armond et a1. June 18, 1940 Appleton Jan. 27, 1942" Lear Feb. 10, 1942 White May 19, 1942 Raskhodoff June 8, 1943 Andrews Aug. 17, 1943 Cunningham May 22, 1945 Fox Mar. 11, 1947 OTHER REFERENCES Ser. No. 863,862, Dolle et al. (A. P. 0.), pub.

May 25, 1943. 

